1. Field of Invention:
The present invention relates to a keyboard provided with an illuminating device for push buttons.
2. Background of Invention:
FIGS. 1(A) and 1(B) are views for showing the structure of a conventional keyboard, the former being a plan view and the latter a sectional view thereof. In the drawings, the reference numerals 1, 2, and 3 indicate a front case of the keyboard, push buttons each bearing a numeral or the like on the surface thereof, and light sources, for example, LEDS (light emitting diodes), respectively.
The numerals 4 and 5 indicate a mechanical switch and a printed circuit substrate for transmitting ON- or OFF-signal emitted by the mechanical switch 4, respectively. The mechanical switch 5 is formed of a bent stainless steel sheet which is fixed to the substrate and, when depressed with sufficient pressure by the push button 2, it is deformed into another configuration to perform a switching operation by mechanical contact.
In the conventional structure as described above, when this kind of keyboard is used at night or in a dark place, a light source 3 located below the push buttons is turned on to enable an operator to read markings on the push buttons and discriminate button 2 from the others. A push button used for the structure described above is a molded product made of a translucent material, for example, acrylic resin, which has a disadvantage in that a spot which is brightly illuminated by the light source is on a limited part of the push button 2 and uneven brightness appear on the surface of the button, thereby causing the indicated marking to be illegible. For improving uneven illumination, the provision of a light source for each button or at the periphery of the button is required, which disadvantageously results in an increase in the number of light sources and power consumption for illumination. Further, for improvement of uneven brightness, there has been a method of reducing loss in light transmission by providing a light guide made of transparent acrylic resin and the like, however, because of a necessity to provide a light guide in addition to the frame retaining the push buttons, this method has been followed by drawbacks such as an increase in the number of parts and resultant difficulty in handling the keyboard.
An object of the present invention is to provide a keyboard capable of brightly illuminating push buttons with a small number of light sources.
Another object of the present invention is to make it possible to illuminate a plurality of push buttons more uniformly.
Still another object of the present invention is to reduce the number of light sources through the application of light reflection from pyramidal reflectors which results in less power consumption for the light sources.
A further object of the present invention is to provide a keyboard in which illumination is made more even by the provision of second wedge-like reflectors.